To use explosive charges to remove plugs that have been temporarily placed to close off a well, a drill hole or the like, is well known. As a rule, such an explosive charge is either placed on top of the inserted plug, but it can also in some cases be placed in the centre of the plug. Today many different mechanisms are used to trigger such explosive charges.
Today's systems with explosive charges leave behind unwanted residues and also the explosive charges constitute a potential risk for the user in the handling of the plug.
Also well known are solutions where one goes down into the well itself and crushes such plugs with mechanical effects, blows or drilling which do not involve explosive charges.
Also known is a solution where individual plug bodies are mounted in their separate seat in the plug, for example as disclosed in the International patent publication WO 2007/108701 (Bjoergum Mekaniske).
This solution is based on a non-compressible fluid being filled between each plug body which at a signal for opening is drained out into a separate atmospheric chamber. By draining this fluid out into the atmospheric chamber the plug elements shall collapse with the help of the hydrostatic pressure. However, if there is a leak in the atmospheric chamber, this would not function as the fluid can not be drained. Another disadvantage with this solution is that the plug construction must be weaker than one wants as it requires that the different plug bodies must be thin enough to rupture with the help of the well pressure only.
The aim of the present invention is to provide a method for removal of the plug without the use of explosives and which does not have the disadvantages described above.
Furthermore it is an aim of the invention to avoid the limitations which today's solutions without explosives place with regard to the plug construction, such as the thickness of the plug element and the risk of damage to the well formation with the opening under pressure higher than the hydrostatic pressure in the well.